Evening Grosbeak: what a flock costs, and why they may never come

The short answer

• Our working figure is 12 to 15 g of in-shell black oil sunflower per bird per day when a flock is leaning on feeders. A flock of 30 is roughly 1 lb of seed a day.
• Black oil and striped sunflower are both top-tier for this species. Striped is the specialist choice: that bill opens it easily while most other feeder birds cannot.
• They need a flat surface. Platform trays and large hoppers are the only two feeder types that work; tubes and small perches are useless to a 60 g flock bird.
• Arrival is irruptive, driven by northern conifer seed crops. Some winters bring dozens, most winters bring none, and no amount of seed changes that.
• Numbers have fallen steeply across the continent since the 1970s, which is why a bird that was a feeder staple for a previous generation is now a notable sighting.

Most feeder birds cost you pennies a week. A flock of Evening Grosbeaks costs real money, and the first time one arrives the feeling is less delight than alarm at how fast the hopper drains. Know the numbers before it happens.

What a flock actually eats#

Start from the seed. Sunflower kernel runs about 584 kcal per 100 g, and in-shell black oil yields roughly 75% kernel by weight, both figures from our own nutrition dataset. A 60 g bird holding its weight through a northern winter needs somewhere around 50 to 60 kcal a day. Run that through the kernel yield and you get our working figure of 12 to 15 g of in-shell black oil per bird per day, about half an ounce, if the flock is taking most of its food from feeders.

Cost uses our working price of $1.35/lb for in-shell black oil. Run your own prices through the seed cost calculator, which also shows why sunflower hearts are not the saving they look like at this volume.

Two caveats. Flocks rarely take everything from feeders, since they also work conifer seed, buds and mountain ash, so many yards see half these numbers. And flocks move: a group may empty your tray for nine days and never return, which makes buying 200 lb in advance a bad bet.

Recognizing one#

An adult male is unmistakable once you have the scale right: a heavy, starling-sized finch, dusky brown head shading to yellow on the body, a broad yellow eyebrow stripe, black wings with a large clean white patch, and a pale conical bill the size of the rest of its face. Females and immatures are silvery gray with a yellowish wash, the same huge bill, and bold black and white wings.

What people mistake them for:

• American Goldfinch. The default wrong guess, since both are yellow and black. A goldfinch weighs about 13 g against the grosbeak's 60 g, so the error only survives because size is hard to judge on a lone bird.
• Pine Grosbeak. Same rough size and northern habits, but rosy red or gray with a small stubby dark bill, no yellow and no white wing patch.
• Female Purple Finch. Gray brown and streaked, a third of the weight, no white wing panels.
• Rose-breasted Grosbeak. Similar bill mass, but an eastern summer bird, never gray and yellow.

How the flock works a tray#

Everything about Evening Grosbeak feeder behavior follows from flock size, and they carry the maximum flocking score in our species data. In practice they arrive as a unit: eight, twenty, forty birds dropping into the same tree within a few seconds, sitting for a minute or two, then coming down together.

• Approach: high and in a group, usually announced by loud ringing call notes before you see anything.
• At the food: shoulder to shoulder, filling every inch. Tray area is what decides how many can feed at once.
• Caching: none. Everything is eaten on the spot, which is what makes the consumption visible.
• Dominance: they simply occupy the tray, and chickadees, finches and siskins wait. Squabbles are frequent but brief, mostly bill-gaping between neighbors.
• Time of day: heaviest in the first two hours after sunrise, second push mid afternoon. A flock vanishing for hours in between is normal.

They shell seed rapidly and drop the husks straight down, so a hull layer builds under the tray fast. Plan on raking, or do not site the tray over a deck.

What to put out, and where#

Skip for this species: Peanuts (in shell), Mealworms, Nectar.

Black oil and striped sunflower are the two top-tier foods, and striped is the interesting one. That bill opens a thick striped hull without effort, while House Sparrows and most small finches cannot, so a tray of striped sunflower hands more of your seed to the grosbeaks and less to everything else. Hearts are eaten readily and are the fastest option in wet weather, but at flock volume the cost difference is severe.

The setup that works:

1. A large platform tray at 4 to 6 ft, ideally 18 in square or bigger, with drainage holes. Surface area is the limiting factor on how many birds feed.
2. A wide-lipped hopper feeder as backup, so the flock is not waiting on you at first light. Capacity matters here more than for any other species.
3. Sweep and refill in the evening, not at 9am. Grosbeaks hit the tray at dawn.
4. Buy in bulk only after they arrive, and store it properly. See storing birdseed.

Irruption winters, and why yours may not be one#

Evening Grosbeaks are not migrants in the ordinary sense. They move in response to food: when conifer seed and mountain-ash crops fail across the boreal forest, flocks push far south, and when crops are good the same birds never leave the North. This is the same mechanism that governs Pine Siskins and redpolls, and the three often move in the same winters.

For a yard in the northern states or southern Canada:

• November to December: first flocks appear if it is a movement year. Watch regional birding reports rather than your own feeder.
• January to March: peak feeder use, and when a flock may settle for weeks.
• April: birds drift back north, often after a brief surge.
• May to October: absent, unless you live in the resident range in the mountain West or northern forest.

In the mountain West they can be present year-round and turn up at feeders at any season, including summer with juveniles in tow.

When they do not come#

The uncomfortable answer is that for most of the continent, this is not a fixable problem.

• Wrong year. In a non-irruption winter, southern and central yards get none. No food, feeder or placement changes that.
• Wrong region. South of roughly the Ohio River and away from the mountains, records are rare even in strong movement years.
• No flat feeder. A yard with only tubes and suet cages can have grosbeaks pass overhead and never stop. This is the one cause fully within your control.
• Empty at dawn. A tray filled at midday misses the main feeding period for days on end.
• Nothing but mixed seed. Milo, wheat and corn are near the bottom of their preference list. Sunflower, or nothing.

The decline behind all of this#

Evening Grosbeaks were an ordinary winter feeder bird across much of the North and Northeast within living memory, and they are not now. Continental monitoring has tracked a steep, sustained decline since the 1970s, and the species carries conservation concern across its range. That is why this page reads differently from other species pages: you are not building a setup that reliably produces this bird, you are being ready for a visit that may come once in several years.

If a flock does arrive, count it and report it. Winter feeder counts are one of the few data sources on a bird that spends most of its life in forest nobody is watching. The wider question of what feeders do and do not do for populations is in do birds depend on feeders.

Frequently asked questions#

How much seed do Evening Grosbeaks eat?

More than any other feeder bird per head. Our working figure, built from the calorie content of sunflower and the winter energy needs of a 60 g bird, is 12 to 15 g of in-shell black oil per bird per day when the flock is feeder-dependent. That is roughly half an ounce each. Thirty birds works out at about 1 lb of seed a day, or around 85 lb across a three-month stay. Flocks rarely take everything from feeders, so real-world consumption is often half that, but it is still the largest seed bill in backyard bird feeding.

Why do Evening Grosbeaks only show up some winters?

They are irruptive. When the conifer and mountain-ash seed crops across the boreal forest fail, flocks move far south of their normal range looking for food; when the crops are good, they stay north and southern feeders see none at all. That cycle is roughly every two to three years but is not reliable, and the size of an irruption varies enormously. Nothing you put in the feeder alters it. What you can control is being ready: sunflower on a tray from November onward.

Are Evening Grosbeaks declining?

Yes. Continental monitoring has tracked a steep, sustained decline since the 1970s, and the species is now a conservation concern across much of its range. Older feeder-watchers in the Northeast remember flocks of fifty as an ordinary winter event; those numbers are not what most yards see now. Suspected pressures include changes in boreal forest and spruce budworm outbreak cycles, collisions, and disease. It is the main reason an irruption year is worth reporting to a monitoring project.

What feeder do Evening Grosbeaks use?

A flat one. They are heavy, they feed shoulder to shoulder, and they will not use a tube or a short perch. A large platform or tray feeder is ideal, and a wide-lipped hopper is the practical alternative if you cannot refill daily. Many people simply spread sunflower on a deck rail or a snow-cleared table when a flock arrives, which works perfectly well as long as it gets swept clean and does not become a wet, fouled surface.

How do I tell an Evening Grosbeak from an American Goldfinch?

Size, mostly. An Evening Grosbeak weighs about 60 g against a goldfinch's 13 g, so a male grosbeak on a tray looks like a goldfinch inflated four times over. Add the bill: a massive pale conical bill, greenish or ivory, unlike anything a goldfinch carries. Males have a bold yellow eyebrow over a dark head and huge white wing patches; females are gray with the same white in the wing. If it is the size of a starling and yellow, it is a grosbeak.

Should I worry about disease with a big flock?

Yes, and it is a genuine practical reason to think about feeder hygiene. Any species that feeds in dense flocks on a shared flat surface raises the risk of transmission, and salmonellosis outbreaks at feeders are usually associated with crowded, seed-fouled trays. Sweep the tray daily, do not let seed sit in wet piles, and clean thoroughly on a schedule. If your state or provincial wildlife agency advises taking feeders down during an outbreak, take them down.

Sources and further reading

1. Evening Grosbeak Cornell Lab of Ornithology, All About Birds Identification, range, irruptive movements and population decline
2. Project FeederWatch Cornell Lab of Ornithology and Birds Canada Winter feeder counts and irruption tracking
3. Birds Canada Birds Canada Boreal forest bird monitoring and conservation status
4. Diseases in Wild Birds USGS National Wildlife Health Center Disease risk where birds congregate at feeders